Olefing production



Sept. 1, 1942.

FRA CNO/v4 TOR oEuYDRoGEA/ATOQ -FRAcr/o/VA r'oA7 G. E. scHM'lTKoNs 2,294,696

oLEFIN PRODUCTION Filed Dec. 14, 1938V m54 rm agem" |NvENT oR y v George E. Schmikons n BY ATTORNEY feed 10 content.

Patented Sept. 1, 1942 4UNITEDSTATES PATENT oFFlcE 2,294,696 n oLEFIN PRODUCTION George E. Schmitkons, Chicago,

Ill., assignor to Standard Oil Company,`Chicago, Ill., av corporation of Indiana Application December 14, 1938, Serial No. 245,549

2 Claims.

This invention relates to an improved process for the production of oleiins from a parainolen mixture and particularly to the production of oleflns from a mixture composed almost entirely of saturated and unsaturated hydrocarbons having the same number of carbon atoms.

In recent years o lens have become more and more valuable because of the commercial success and expansion of synthetic processes for converting them into various chemical products, hydrocarbon motor fuels and lubricants, etc. This is .particularly true of'the so-called normally gase- Ybe chiefly ethylene, or propylene, or butylenes,

but not mixtures of any. two, or all three, of the olens. Y

One source of olens for'such processes as have been mentioned is the gases obtained in the cracking of oils. from the production of hydrocarbons by the Fischer-Tropsch process, the off-gases from se lective polymerization, etc. Such gases, however, contain in varying amounts the corresponding saturated hydrocarbons such as ethane, propane and the butanes together with methane and hydrogen, but they may be and often are separated into fractions, each fraction of which, excluding hydrogenand methane, will predominate in two, three, or four carbon atom constituents. It has been found that the parainic constituents of such gases do not react with the same ease olens and, in some cases, even deter or prevent the olens from reacting to the best advantage.

It is an object of my invention to convert gas mixtures predominating in hydrocarbons having Other sources include the gases (Cl. S60-683) tion of parans from olefins having the same number of carbon atoms by means of azeotropic distillation,v the conversion of the parairns to olefins by idehydrogenation, preferably catalytic dehydrogenation, and the separation of the converted from the unconverted parafhns by the original azeotropic distillation means.

Paraflins can be separated from the corresponding olens by adding to the mixed parafiinsolens a third substance which forms an azeotrope. The azeotropes of the parains and olefns show a greater spread in boiling point than the original parans and oleiins, and the azeotropes can therefore be separated by distillation.

as the the same number of carbon atoms containing both parallin's and olens, to a predominantly oleiinic product having the samecarbon atom It is another object of my invention to provide an integrated process for the conversion .of paraffin hydrocarbons to olen'hydrocarbons and the separation of the latter in relatively pure form. A further object of my invention is to provide a novel and economical method of preparing an olenic feed stock for hydrocarbon or other syntheses. Other and more -detailed objects of my invention will become apparent as the description thereof proceeds.

In brief my invention contemplates the separa- For example, the various butanes and butenes, all of which may be found in a butane cut from cracking still gas, have the following boiling points:

4Isbutane 12.4 N-butane 0.6 Isobutylene 6.7 2-butene (trans) 1.3 l-buteno -6.7 2-butene (cis) 3.7

C. Azeotrope of isobutane -24 ,n Azeotrope of N-butane 18. Azeotrope of l-butane -16 Azeotrope of isobutylene -14 Azeotrope of 2-butene (trans) -14 Azeotrope of 2butene (cis) -13 There is a spread of 2 C. between the highest boiling parailin azeotrope and the lowest boiling olefin azeotrope, and hence separation by fracti0na1 distiuation is possible.

Substances other than sulfur dioxide may be used to form azeotropic mixtures. 4For example, Deansley, in his United States `Patent No. A1,866,800 describes the separation of butanes and butenes by azeotropic distillation, using liquid ammonia or methylamine, to give a yield of 96% butene from the butenes present. Other sub stances may also be used, and since the particular substance to beadded to the paraiin-olen mixture to form azeotropes is no part of my invention, they will' hereinafter be azeotropic agents."

The operation of my process will be understood from the `following description and the accomreferred to y as water vapor.

dominantly hydrocarbons of the same number of carbon atoms from anysuitable source, as for example plant butane from the stabilization of gasoline, enters through line I and is' joined by an azeotropic agent from line -I I. The two substances are thoroughly mixed in mixer I2 which may be any suitable device for intimately contacting the two streams.

'I'he combined streams enter fractionating tower I4 by line I3 where they are heated by heater I5 which may be a closed steam coil or any other suitable means. The paraflins plus the azeotropic agent are distilled overhead and the oleiins plus` the remaining azeotropic agent remain as a bottom fraction. 'I'his latter mixture is withdrawn through valved line I6, cooled if desired in cooler I'I, and transferred to separator `I8 by line I9. Since phase separation of the azeotropic agent from the oleflns cannot be accomplished by cooling alone, as can be done with parafn azeotropes, I prefer to use a sep-` arating agent. This separating agent may be water if the azeotropic agent is relatively soluble therein, or it may be an aqueous solution of a compound with which the azeotropic agent forms a water soluble complex, easily decomposable to yield the azeotropic agent unchanged. -Such compounds include the water soluble organic amines, such as pyridine and triethanol amine, alkali thiocyanates, vsuch as sodium thiocyanate and potassium thiocyanate, and the alkali iodides,A

such as potassium iodide and sodium iodide, if the azeotropic agent is sulfur dioxide.

To obtain the separation of the azeotropic agent (e. g., SO2) and the olefins, the separating degree that a ready separation between the parailin and the azeotropic agent may be' accomplished. The cold liquor is sent to separator 28 through line 29. In separator 28 a very substantial separation of the parailin from the azeotropic agent takes place and the azeotropic agent is withdrawn through line 30 and a part thereof is returned to the top of fractionator I4 through line 3| to act as reflux in the distillation. The remainder of the azeotropic agent may be withdrawn through line 32 and returned to the treating system through line I I, or may be withdrawn from the system entirely through line 33.

The paraiilns from separator 28 are fed to washer 34 by line 35 wherein the traces of azeotropic agent remaining are removed. The washing medium may be any suitable substance, for

example, water, dilute caustic, dilute acid, etc.,

which will remove the azeotropic agent from the parafiins and the selection of this medium will be governed entirely by the nature of the azeo- Atropic agent. The -washing medium enters through line 36 and is discharged through line 31.

The paraflins from washer 34 are led through line 38 to heater 39 -where they are raised to a temperature suitable for dehydrogenation. The heated gases pass from heater 39 through line 40 to dehydrogenator 4I which is iilled with any suitable catalytic material as will be discussed later. The dehydrogenated product is withdrawn through line 42 and sent to fractionator 43 after having been cooled by cooler .44.

In fractionator 43, having reux means 41 and heating means 48, the light gases, for example.

hydrogen and methane, and any ethane and propane with their accompanying oleiins, are separated and discharged from the system through line 45, while'the dehydrogenated butanes and agent, in'an aqueous medium, is added to separator I8 through line 60 lwhich joins line I9.

The sulfur dioxideforms a loose complex with the separating agent, it is believed, and the complex is withdrawn from separator I8' through line 2l and directed to still 5I, wherein it is heated by heating means 52 suillciently to decompose the complex and drive of! the sulfur dioxide as a gas. 'I'he temperature necessary to decompose the complex will vary with the separating agent chosen, but in all cases it should be less than the boiling point of water to avoid contaminating the azeotropic agent with any great amount of 'I'he 'azeotropic agent passes overhead .through line 2i, is dried if necessary (by means not shown) and returned to the azeotropic distillation -step through line I I. The separating agent is withdrawn from still 3| and returned to separator I 8 for reuse throughline 53, which joins line [50, or may be withdrawn from the system through line i4.

The oleiins are withdrawn through line 23 and to Ia washing step (not shown) where any remaining traces of the azeotropic agent may be removed and the olen transferred to a polymerization unit, an alkylatiorn unit, an. aleohol/ manufacturing process, or any other process in which the use of highly concentrated AJblenns. is particularly advantageous.

4The paramns plus the azeotropic agent pass tion at approximately 0 F. to 125 F. and at an absolute pressure of from 15 to 150 pounds perv overhead rom fractionator I4 through line 24 and condenser 2l where they are reduced to a liquid state. From condenser 23 they pass any undehydrogenated butanes are withdrawn by line 46 and returned to the azeotropic distillation system through line I0 where they join the fresh feed.

It may be desirable to use my process for the conversion of natural gas to oleilns. Since natural gas contains a preponderance of paramns and only small amoun'ts of oletlns, it is necessary to subject it tot dehydrogenation before azeotropic distillation. In this event, the hydrocarbon mixture of paramns and oleiins preferably having four carbon atoms to the molecule, may b`e injected through line 49 just prior to heater 33. and the dehydrogenated .products cycled to the azeotropic distillation step, where the oleilns formed are separated from the unconverted paramns, and the paraflinsrecycled to' the deny-,-

drogenation step.- Other normally gaseous hydrocarbons having four carbon atoms and predominantly paramnic, such as oil-gases from alkylation, etc., would be injected at this point.

The typical operation will serve to illustrate my process. A plant butane c`ut obtained from the gases from the cracking of oil consists of both normal and isobutane, as well as isobutylene and' land 2-butens. This may be mixed with sulfur dioxide in the proper proportions to obtain the best separation which generally requires an excess of sulfur dioxide over that required to form the azeotropes and the mixture subjected to distilla-` square inch. The butenezeotropes having aj higher boiling. point than the azeotropes of butane and isobutane will collect in the bottom of fractionator I4. After cooling and removing the sulfurdioxide', it will be found that approxibutenes from the azeotropic distillation (whichterm Vis intended to include isobutylene) will be found to be a most excellent-feedstock for polymerization to gasoline using as a' catalyst such-well known agents as phosphoric acid on I kieselguhr or boroniiuoride. It is also an excellent feed stock forpolymerization at lowtemboron luoride to high molecular weight resins.

" If" desirable Athe 'isobutylene present may be selectively polymerized to lyield -high octane gasoline and the'normal butenes remaining may then be isome'rized over such catalysts asphosphorus pentoxide or phosphoric acidon kieselghurat' other temperatures, pressures and time ci contact. Such -iso'merized olens may then tbe returned to the selective polymerization step Vfor polymerization of high octane gasoiines. Other uses for oleiins will readily occur to thoseskilled in the art, and my invention .is not directed to' the speciiic utilization oi.' this valuable source 'Ifhebutanesplussulfur dioxide in the formo! azeotropes 'are thoroughly cooled to permit the separation of the butanesand the sulfur dioxide, epd the sulfur dioxide returned part tothe fracl gfoof said parailinic hydrocarbons to olenic hydro;

tionatorto" act as reflux andaid in distillation which separates the butane azeotropes from the.

butene aze'otropes, and partfreturned to be mixed with the incoming plant butanejfeed. In this manner the amountor sulfur dioxide required is reduced to a minimum and byl using a part'as redux o better fractionation vis obtained. ,f

The separated butanes are washed to remove sulfur dioxide and are'then heatedto from' about 850 to about 1000 F. in heater 39.

ted gases are then passed to a catalyst chamber ll oxides,

53,1 l i. In a process for the production of normally:

.dojturning lled with a dehydrogenating ca* talyst. Any suitable catalyst may be employed: --chroinic oxide -gels, mixed alumina-chromium metal chromites, mixed alumina-"metal The above description is by of and not by way of limitation and my invention should not' be limited thereby but only insofar as is set orth in the appended claims.`

claim:

gaseous oleiins from afhydrocarbon mixture com prising normally gaseous paraitlnic-` and oleiinic atoms, the steps comprising adding to said hyperatures with such gaseous metallic-bandes as v drocarbon mixture sulfur dioxide to form an azeotropic mixture therewith,

dominantly paranic azeotropes and a fraction Y cooling said paraiiinic azeotrope until a separation -of paraiiinic hydrocarbons and sulfur dioxide is obtained, separating said paraiiinic hydrocarbons and said sulfur dioxide.` cooling said oleiinic lazeotrope, adding to said cooled olenic azeotrope Y a separating agent comprising an aqueous. solu- 'tionof a compound selected from the group consisting oi water-soluble organic amines, alkali thiocyanates andalkali iodides, recovering oleiinic hydrocarbons present in saidvoleni'a'zeo- V trope from sulfur dioxide carbons having the same number' of carbon. atoms and to produce a small amount of hydrocarbonsv bon mixture, separating said hydrocarbons having a lesser number of 'carbon atoms formed in' said delydrogenation from said olenic hydro. carbons having the same number of carbon atoms as said separated parailinic hydrocarbons, resaid oleiinic-hydrocarbons and uncon- .verted parailinic hydrocarbons tol be mixed with said sulfur dioxide `and separating said uncon- 't .verted paraiinicv hydrocarbons from said olennic Y hydrocarbons by azeotropic distillation'.

chromites. metals or metal oxides supported on- .2. A- process for the production of butylenea metal chromites. etc. In this manner appro mately of the' butanes may beconverted to butenes and'isobutylene. In addition a certain amount of methane and higher willlbe formed as well as the hydrogen from the dehydrogenatlOlL These gases are separated from the butanebutene mixture in iractionator I3 sind discharged fr0!!! the system, The paraiiineoleiin mixture resulting iromthe dehydrogenation and fractionation is' returned to thev azeotropic system wherev itjoins fresh feed and oleiins formed are in the manner "described Previously.

i n vm be' seen-that by my process-1 obtain o yield of oleiins suitable for the. synthesis of higherhydrocarbons by a completely integrated andcoordinated s ystem,. no part of whl; can serve toaccomplish my improved rethe discardoLgaseawhichmay'be conependently. Azeotropic distillation alone vorname/valuable and usefmform.- anejos.-

by itself is not suiilcicntly' cilinvlcte toconvertallofthebutanes to xox-m. ,By my process" alli-or the' pai-amm are eventually romanos-with practically'.

-no loss, thereby providing "avoidable f from a mixture of. butanes and buty1enes,compris .ing adding to said mixture sulfur dioxide to iorm an azeotropicmixture, distilling said azetropic into afraction containing predominantly, so butane azeotropes and a fraction containing pre'- 'dominantly butylene azeotropes, cooling said bu-j A tane azeotropes until a separation oi.' butanes and sulfur dioxide isobtained, separating vsaid butanes and said sulfur dioxide, cooling saidlmtyl# .v

ene azeotropes, adding to said cooled butylene azeotropes aseparating agentvcomprising -an aqueous solution of a compound selected -from the osent.

tones, and recycling said lastmentioned butyl? said unconverted butancsto Vtronic distillation steil-v i hydrocarbons having the same number of carbon said azeo. tropic mixture into a fraction containing 4pre-A 

